An ecclesiologist, Gaillardetz is an expert on ecumenical councils, particularly the Second Vatican Council. He recently co-authored Keys to the Council: Unlocking the Teaching of Vatican II, which presents a less intimidating and more accessible introduction to the vision of the Vatican II. His newest publication is a volume he edited titled When the Magisterium Intervenes: The Magisterium and Theologians in Today's Church, a collection of papers by leading Catholic scholars on the Church’s official teaching authority in a postmodern world.

Gaillardetz has been honored for his writings by the Catholic Press Association and received the Sophia Award for theological excellence from Washington Theological Union in Washington D.C.

With a membership of more than 1300, the CTSA is the principal association of Catholic theologians in North America and the largest professional society of theologians in the world. Active members of the society hold a doctorate in theology or a related discipline. Founded in 1946, the CTSA promotes theological research in the Roman Catholic tradition that is attentive to contemporary problems faced by the Church and the world.